1. Field of the Invention
The present invention relates to a multi-view three-dimensional (3D) image display apparatus, and more particularly, to a multi-view 3D image display apparatus which may form a modified common viewing zone corresponding to an intermediate concept of a multi-view 3D image display apparatus and an integrated 3D image display apparatus, or equalize or reduce an amount of crosstalk using a predetermined region after the common viewing zone created at an optimum viewing distance (OVD) of the multi-view 3D image display apparatus.
2. Discussion of Related Art
An autostereoscopic multi-view three-dimensional (3D) image display apparatus may employ a method using an optical plate such as a lenticular lens, a parallax barrier, or the like, or a method using a line light source array, for forming a viewing zone. However, in the 3D image display apparatus using the parallax barrier, the lenticular lens, or the line light source array for forming the viewing zone, in principle, even within the same viewing zone, a crosstalk phenomenon in which a distribution of light and an image of an adjacent viewing zone partially overlap due to movement of the eyes may occur. Thus, it is difficult to implement natural 3D images while a viewer is moving, thereby giving the viewer an uncomfortable feeling.
In the multi-view 3D image display apparatus, an optical plate is designed in such a manner that viewpoint images arranged in pixels on a display panel converge at a specific position at an optimum viewing distance (OVD). Viewing zone arrangement from the position at the OVD designed by such a 3D image design method is referred to as common viewing zone formation. In order to form such a common viewing zone, a period (T) of the optical plate should be designed to be smaller than a value obtained by multiplying a pixel size (Wp) of the display panel by the number of viewpoints (N) of the display panel. That is, “T<Wp*N” should be satisfied.
FIG. 1 is a conceptual diagram illustrating a principle of a common viewing zone of a general multi-view 3D image display apparatus. Referring to FIG. 1, in order to implement 3D images, an optical plate such as a lenticular lens or a parallax barrier may be arranged on the front of a display panel. By the optical plate designed according to the pixel size and the number of viewpoints of the display panel, a common viewing zone according to the designed number of viewpoints may be implemented at the OVD position. In FIG. 1, an example in which a common viewing zone is formed according to a four-viewpoint design is shown. However, such a general multi-view 3D image display apparatus may have a problem of a nonuniform amount of crosstalk that changes with horizontal movement (movement parallel to the display panel) of the viewer. Accordingly, only when both pupils of the viewer's eyes are located in the center of a viewpoint may the viewer experience a minimized amount of crosstalk. In addition, there is also a problem of an absolute value of the minimized crosstalk quantity being larger than a general amount of crosstalk in a method using glasses.
More specifically, the cause of these problems will be explained with reference to FIG. 2, which shows light intensity distribution and crosstalk distribution for each viewing zone according to a horizontal position of a viewer in the general multi-view 3D image display apparatus. FIG. 2 illustrates an example of a general multi-view 3D design using the parallax barrier, in which the number of viewpoints is 4, a viewpoint interval is 32.5 mm, and a tilt angle from a vertical direction of an opening of the parallax barrier is tan−1 (⅓) (rad). As shown in FIG. 2, viewing zone characteristics of the general multi-view 3D image display apparatus have a problem in that brightness of a corresponding viewpoint image changes depending on the horizontal position of the viewer. As an example, the brightness of the corresponding viewpoint image may be the highest when a pupil (left eye or right eye) of the viewer is positioned at a position A, and the brightness of the corresponding viewpoint image may be reduced when the pupil is positioned at the other positions (position B or C). In addition, the amount of crosstalk with adjacent viewpoints may change depending on the horizontal position. For example, crosstalk may be minimized when a pupil of the viewer is positioned at the position A (the center of a corresponding viewing zone), and may significantly increase as the pupil deviates from the center of the viewing zone. Thus, when a pupil of the viewer is positioned at a position C, the viewer may experience a maximum amount of crosstalk. In addition, an amount of crosstalk of about 20% to 30% may be generated even when the pupil of the viewer is positioned at the center of the viewing zone, and therefore there is a disadvantage of the amount of crosstalk being at least four times larger than in a general glasses type 3D image display apparatus (average amount of crosstalk is 5% or less). In particular, when the pupil of one of the viewer's eyes is positioned in a central viewing zone, and the other is positioned in a side viewing zone, the viewer may experience inverse stereoscopic vision.
As another method of arranging viewpoint images in a space that contrasts with the multi-view 3D image display apparatus, a 3D image display apparatus employing an integral photography method may be used. FIG. 3 is a conceptual diagram for explaining a phenomenon of viewing zone formation of the 3D image display apparatus employing a general integral photography method. For the 3D image display apparatus employing the integral photography method, initially a full parallax disparity method using a two-dimensional (2D) lens array was researched in depth, but now a 3D image display apparatus employing a one-dimensional integral photography method that provides only horizontal parallax disparity information employing a lenticular lens sheet used in the multi-view 3D image display apparatus is being researched. A period (T) of the lenticular lens used in the 3D image display apparatus employing the one-dimensional integral photography method may be the product of a pixel size (Wp) and the number of viewpoints (N) of a display (T=Wp*N). That is, the period (T) of the lenticular lens may be an integer multiple (N) of the pixel size (Wp) of the display. This is different from the requirement that the period (T) of the lenticular lens used in the general multi-view 3D image display apparatus be smaller than the integer multiple (the number of viewpoints T) of the pixel size (Wp) (that is, T<Wp*N). Due to this difference in design, an OVD that forms the common viewing zone exists at a finite distance in the multi-view 3D image display apparatus, but the common viewing zone is not formed in the 3D image display apparatus employing one-dimensional integral photography method, and therefore the OVD exists at an infinite distance conceptually. Viewing zones of a viewpoint image formed from one period (typically corresponding to a pitch of the lenticular lens) of a set of pixels in which the viewpoint image is arranged in the display panel and a specific optical plate are formed symmetrically with the arrangement of pixels in which the viewpoint image is arranged, about a direction perpendicular to the display panel. Thus, such viewing zones are formed in different positions from viewing zones of a viewpoint image formed from one period of a set of adjacent pixels located in a different position and an adjacent optical plate located in a different position. Such a viewing zone formation method is referred to as parallel viewing zone formation and contrasts with the common viewing zone formation used in the general multi-view 3D image display apparatus.
In such an integral photography method, an amount of crosstalk within a central viewing zone is uniform, but as shown in FIG. 3, there are disadvantages in that a range of the central viewing zone is reduced compared to the multi-view method and an average amount of crosstalk within the central viewing zone is large.
As described above, crosstalk that occurs in the autostereoscopic 3D image display apparatus is an important issue in commercialization. Accordingly, there is demand for a method of greatly reducing crosstalk compared to the existing method, and for an autostereoscopic 3D image display apparatus that can realize the same level of crosstalk as the glasses type method which is not sensitive to a position of a viewer.